Previously known joint mechanisms for finger joints and wrists, for instance, generally comprise a pad of resilient material which has been secured in suitable manner between fixtures anchored in the bone and/or tissue on each side of the natural joint which has been removed--see for instance U.S. Pat. application Ser. No. 406,586 filed Sep. 13, 1989 by Per-Ingvar Branemark and issued on Nov. 5, 1991 as U.S. Pat. No. 5,062,851 entitled Anchoring Element For Supporting a Joint Mechanism of a Finer or Other Reconstructed Joint.
However, in practice such a resilient pad has proved to have certain limitations both as to general strength and also since it lacks certain joint functions--controllable bending, lateral movement, particularly in the case of wrists, effective "locking" when under load, e.g. when the palm of the hand is used as support, etc.